Several factors affect how your coffee tastes, and one of the most significant of these factors is the manner in which the coffee is processed. While the end result in coffee processing is usually to separate the beans from the outer layers, the method used has a huge impact on the quality of the beverage.
Coffee processing methods can be grouped into four; washed processing, natural processing, wet-hulled processing, and honey processing. The producer has to consider the prevailing environmental conditions, desired flavor, and profitability when deciding on the methods to use.
What does coffee processing entail?
Coffee processing entails drying coffee cherries and removing the external layers to end up with coffee beans that can then be roasted, ground, and brewed to make a coffee beverage. Coffee processing is one of several factors that determine the flavor of the coffee. As such, you should choose a processing method that will bring out the type of flavor that you desire.
A coffee fruit has various layers including the skin, pulp, parchment, silverskin, and seed. The coffee cherries have to be dried and the layers removed down to the silverskin to get roastable coffee beans. Not only does the chosen processing method affect the taste and flavor of the end drink, but it also affects its acidity.
Note: The silverskin refers to the layer beneath the mucilage that surrounds the coffee seed.
Coffee Processing Methods
Coffee can be processed in four different ways including washed processing, natural processing, wet-hulled processing, and honey processing.
Washed processing
In washed processing, the seeds are separated from the pulp using depulpers before being dried. The process is preceded by a cherry-picking process to pick out the coffee fruits that meet the desired ripeness and density levels.
After the sorted coffee seeds are separated from the skin and pulp, they’re passed through water tanks to wash off any remaining mucilage still on them. Finally, the coffee seeds are sun-dried before they can be ready for roasting.
Washed processing is a fast and simple way of processing coffee. What’s more, it lends the coffee a distinctive flavor. Wash-processed coffee is noticeably crispier than natural-processed coffee, while also boasting a lighter consistency. What’s more, this type of coffee has a bright tone that complements its sweetness.
However, this method is not environmentally sustainable, as lots of water is required to wash all of the mucilage off the coffee beans. Still, you can offset this disadvantage by rebalancing the Ph of the used water and reusing it for subsequent washing cycles.
Note: Washed processing also contributes to poor resource sustainability, as lots of material and technology resources are required to build and maintain the washing stations. Meanwhile, the human resources required to operate the washing stations contribute to added operational costs.
Natural processing
Natural coffee processing, also known as dry processing, is a coffee processing method whereby fresh coffee cherries are laid and put on a platform to dry. This is the oldest method of processing coffee beans and requires the fruits to be dried before the seeds are separated from the pulp.
The entire process takes 3-6 weeks. As the coffee fruits dry and ferment during this period, the juices from the pulp seep into the coffee beans, lending them a rich, distinctive flavor. During the drying duration, the coffee cherries should be continually raked and spun to keep them from spoiling.
Note: After the coffee has been dried for the required duration, the seeds are detached from the skin and pulp using a machine.
The lengthy processing period results in natural-processed coffee boasting a deep and intricate flavor. This kind of coffee is also heavily bodied. The sweet, juicy, and syrupy flavor can also be attributed to the fact that the seeds are fermented with the outer layers still attached to them.
On the downside, it’s hard to achieve a consistent flavor with natural-processed coffee, since the fermentation process for one batch can’t be replicated for the next one. Additionally, it’s possible to end up with mold infestation if you don’t rake and rotate the cherries as frequently as you should.
Wet hulled processing
In wet-hulled processing (also referred to as semi-washed processing), after the seeds are removed from the cherries using a depulper, they’re not taken through washing tanks to remove the mucilage. The seeds don’t go through the drying stage immediately after de-pulping, either.
Instead, they’re stored in plastic tanks where the mucilage develops into a thick encapsulation. Afterward, the mucilage, as well as the parchment, is removed through a process known as hulling. It’s only after hulling that the coffee seeds are laid out in the sun to dry.
This coffee processing method is best used in humid weather conditions where proper drying can be hard to achieve. It cuts the drying time in half, making it a quick way of processing coffee. Wet-hulled coffee has a savory flavor and is heavy-bodied.
Honey processing
Honey coffee processing is a hybrid of both wash processing and natural processing methods. In this method, the coffee seeds are depulped before they fully dry out. Then, instead of being passed through washing tanks to remove the mucilage, they’re laid out to sun-dry with the mucilage still intact.
The mucilage dries on the seeds and is what lends this type of coffee its unique flavor. As the seeds dry out, they’re rotated to prevent mold infestation.
Note: In some cases, machines are used to control the amount of mucilage left on the coffee beans.
Since this processing method is a blend of two other methods, the flavor of honey-processed coffee is a fusion of the flavors of wash-processed coffee and natural-processed coffee. It has a rich, sweet, syrupy taste and is clean-bodied. The mucilage also makes it more acidic, but it’s mellower compared to wash-processed coffee.
Note: Compared to the other methods on this list, honey processing is a more demanding way of processing coffee.
What influences the production method to use?
Before deciding which processing method to use, the producer considers various issues including the profitability of the method, the environmental conditions, and the desired flavor that they’re looking to achieve.
Rain, for instance, can deter a producer from using the natural processing methods, as the coffee beans may start splitting. Meanwhile, when weather conditions are dry, the sugars won’t get washed away, making it a good time to use natural processing or honey processing methods.
The sugar content of the coffee also determines the best processing method. Coffees with high sugar content are best processed using washed processing, honey processing, or natural processing to bring out the sweet flavor.
Note: Coffee processors use refractometers to measure the sugar content of coffee.
What happens after processing coffee?
After the coffee has been processed and dried, the next stage is milling the parchment coffee. The coffee beans are then graded and sorted by weight and size. At this stage, the beans are also reviewed for quality, with coffee beans that have imperfections being removed. Finally, the coffee beans are packed and exported.
References
Journal of Food Quality: Coffee Drying and Processing Method Influence Quality of Arabica Coffee Varieties (Coffee arabica L.) at Gomma I and Limmu Kossa, Southwest Ethiopia
